Problem: Solve for $a$ : $a + 30 = 22$
Explanation: Subtract $30$ from both sides: $ \begin{eqnarray} \\ a + 30 &=& 22 \\ \\ {-30} && {-30} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{30 + a} &\hphantom{=}& \hphantom{22} \\ a &=& 22 {- 30} \\ \end{eqnarray} $ Simplify. $ a = -8$